四年级上册数学 乘法分配律重点解析


简介:
类型一:(注意:一定要括号外的数分别乘括号里的两个数,再把积相加) (40+8)×25 =40×25+8×25 =1000+200 =1200 36×(100+50) =36×100+36×50 =3600+1800 =5400 类型二:(注意:两个积中相同的因数只能写一次) 36×34+36×66 =36×(34+66) =36×100 =3600 75×23+25×23 =23×(75+25) =23×100 =2300 63×43+57×63 =63×(43+57) =63×100 =6300 类型三:(提示:把102看作100+2;81看作80+1,再用乘法分配律) 78×102 =78×(100+2) =78×100+78×2 =7800+156 =7956 75×41 =75×(40+1) =75×40+75 =3000+75 =3075 125×81 =125×(80+1) =125×80+125×1 =10000+125 =10125